If that’s the way things go, subscription, there aught to be insurance coverage built into that. It’s required anyway and the extent to which a driver relies on SD, and has to pay a sub, then it’s the SD responsible for accidents, not in full but part, and insurance can reflect that as well. But if the two are inextricable as a requirement anyway, there should be baked in standardized procedures for “things have gone wrong, which was a known inevitability, and this is the framework for handling it.”